Sprayer systems with different designs are used in agriculture during treatment of grain to distribute liquids or mixtures, such as pesticides, herbicides, fertilizers or other liquid chemicals. One problem with many designs is that the liquid to be sprayed or distributed must be agitated or always kept in motion by flow so that demixing or deposits do not occur in the sprayer system. Demixing and deposits can cause clogging of the sprayer system and nonuniform concentration of the liquid or mixture.
Prior art attempts to overcome demixing and deposits typically include circulation systems wherein the liquid being sprayed is circulated, especially during interruptions in the spraying operation or sectional operations, so that continuous liquid movement is present in all lines of the sprayer system. Such systems often have separately controlled spray nozzles, such as pneumatically or electrically flow interrupting spray nozzles to avoid output of spray liquid at the spray nozzles when the liquid must be passed by the nozzles for circulation. Such spray nozzle systems, however, require much maintenance and attention and are costly.
A circulation system is disclosed, for example, in DE 34 01 734, in which a spray device contains a recirculation line wherein the liquid being sprayed is kept in continuous circulation. A shortcoming with such a system is that circulation no longer occurs during interruptions in spraying, and deposits can occur in the liquid remaining in the sprayer system.
The spraying machine disclosed in FR 2 678 181 is representative of another type of system in which liquid circulation can be produced using a recirculation line and a control valve located in the recirculation line. In this type, liquid circulation is provided by opening the control valve when the spray operation is discontinued or interrupted. A shortcoming of such a system is that no liquid circulation is made possible during the spray operation, so that liquid remaining in the recirculation line can experience precipitation and demixing. In addition, the spray nozzles cannot be operated separately from each other to permit sectional operation.
A sprayer system is also disclosed in a brochure of the Amazone company with the masthead MI 126/S 233 (D) 04.02, referred to as a pressure circulation system (PCS) for towed field spraying. In this system, circulation is implemented by reversal of the flow direction, wherein a three way valve is contained between a feed line, a recirculation line and a spray nozzle system. The spray nozzle system is designed as a circulation line, and the direction of flow in the spray nozzle system can be reversed by controlling the three way valve. A drawback with the PCS type of system is that during spray operation, no liquid movement occurs in a portion of the spray nozzle system circulation line, and particles can deposit in this portion. In addition, this system requires additional hardware which increases maintenance requirements and expense.
EP 820 224 B1 discloses another type of spraying machine that permits circulation of the liquid during interruption in spraying via recirculation line structure provided with partial vacuum and a feed line in addition to the main feed line. A drawback with this type of machine is that, during spraying with sectional operation, the liquid remaining in the recirculation line and the additional feed line does not circulate since a vacuum can only be generated during an interruption in spraying.
The problem to be solved by the invention is seen in the fact that the known sprayer systems are demanding and costly and/or permit no circulation of the spray liquid during an interruption in spraying or sectional operation.